Daily Overview: — Greetings, dear readers, and welcome to today’s rapid overview of research in the field of nickel-based superconductors. Today’s highlights focus on the electronic structure and superconducting mechanisms of mixed Ruddlesden-Popper nickelates and infinite-layer nickelates. In [1], through fluctuation exchange approximation analysis, it is found that hole doping in La₃Ni₂O₇ thin films can enhance the Fermi surface nesting-driven s±-wave pairing, providing a theoretical pathway for raising the superconducting transition temperature. In [2], systematic measurements of the superfluid density in Nd₁₋ₓSrₓNiO₂ thin films reveal the critical role of phase fluctuations in limiting the critical temperature, and uncover a strong coupling between the Nd 4f magnetic moments and the superfluid, with two-dimensional BKT behavior dominating the superconducting transition. These findings deepen our understanding of the pairing mechanisms and superfluid response in these two types of nickel-based superconductors. arXiv submission processing window: 2026-03-09 00:00 to 2026-03-09 00:00 UTC.

1. Possible Enhancement of Superconductivity in Ambient-Pressure La$_3$Ni$_2$O$_7$ Thin Film

Summary: This study systematically analyzes a two-site, two-orbital model of the La₃Ni₂O₇ thin-film superconductor under ambient pressure within a weakly correlated system, employing the fluctuation exchange (FLEX) approximation, with a focus on the influence of hole doping on superconducting properties. Through a detailed examination of the Fermi surface topology, it is found that when the δ pocket, formed by the d_{z²} antibonding orbital, emerges near the Γ point, the nesting between the δ and γ pockets, together with the nesting between the α and β pockets, collectively enhances s±-wave pairing at the corresponding wave vectors. The study further proposes that this enhancement mechanism of spin-fluctuation-induced pairing, driven by Fermi surface nesting, may provide a feasible route to raising the superconducting transition temperature. This work offers theoretical guidance for understanding the pairing mechanism of nickel-based thin-film superconductors under ambient pressure and for exploring higher-performance superconducting materials.

2. Evolution of the Superfluid Density in Infinite-Layer Nickelates

Summary: By systematically measuring the superfluid density of Nd₁₋ₓSrₓNiO₂ thin films as a function of doping and temperature, it is found that the superfluid stiffness is weak and exhibits an approximately square-root relationship with the critical temperature Tc, indicating that phase fluctuations play a key role in limiting Tc. Meanwhile, a significant reduction in superfluid density is observed in the low-temperature region, an effect far beyond paramagnetic explanations, suggesting strong coupling between the magnetic moments of Nd 4f electrons and the superfluid, with the magnetic ordering temperature linearly extrapolating to x=0.29. Furthermore, near the transition, the superfluid density shows a BKT-type accelerated decrease, indicating that the unbinding of two-dimensional vortex-antivortex pairs governs the superconducting transition. These results provide key experimental evidence for phase fluctuation-limited Tc and the substantial influence of rare-earth magnetism on the superfluid in nickelate superconductors.